1. Field of the Invention
The present invention relates to an inorganic biomaterial which is useful as an implant material for artificial bones, dental implants, etc., as well as to a process for producing said inorganic biomaterial.
2. Description of Prior Art
As so-called bioactive ceramics capable of forming a chemical bonding with bones, there are known sintered apatite and a crystallized glass of Na.sub.2 O-K.sub.2 O-MgO-CaO-SiO.sub.2 -P.sub.2 O.sub.5 type. As the bioactive ceramic, there is further known a crystallized glass obtained by grinding a MgO-CaO-P.sub.2 O.sub.5 -SiO.sub.2 type glass to a particle size of larger (finer) than 200 meshes, molding the resulting glass powder into a desired shape, heat-treating the resulting molding at a temperature range in which the glass powder is sintered, and then heat-treating the resulting sintered product at a temperature range in which an apatite crystal [Ca.sub.10 (PO.sub.4).sub.6 (O.sub.0.5, F).sub.2 ] and a wollastonite crystal [CaSiO.sub.3 ] are precipitated [Japanese Patent Application (Laid-Open) No. 191252/1982]. In this crystallized glass, the apatite crystal contributes to the biocompatibility and the wollastonite crystal contributes to the mechanical strength. Hence, to increase the mechanical strength of the crystallized glass, it is desirable to increase the content of the wollastonite crystal. In this connection, there is furthermore known a crystallized glass obtained by increasing the SiO.sub.2 content to form a larger amount of the wollastonite crystal precipitated.
As to the bending strength, the sintered apatite has about 1,000 to 1,400 kg/cm.sup.2 ; the Na.sub.2 O-K.sub.2 O-MgO-CaO-SiO.sub.2 -P.sub.2 O.sub.5 type crystallized glass about 1,000 to 1,500 kg/cm.sup.2 ; the MgO-CaO-P.sub.2 O.sub.5 -SiO.sub.2 type crystallized glass about 1,200 to 1,400 kg/cm.sup.2. The CaO-P.sub.2 O.sub.5 -SiO.sub.2 type or CaO-P.sub.2 O.sub.5 -SiO.sub.2 -(MgO, Y.sub.2 O.sub.3) type crystallized glass containing a larger amount of the wollastonite crystal has a high bending strength of 1,700 to 2,300 kg/cm.sup.2. However, these values are not yet fully satisfactory from the standpoint that the above materials are used in applications such as artificial bones and dental implants. Hence, a material of higher strength is desired.
Accordingly, an object of the present invention is to provide an inorganic biomaterial having excellent biocompatibility and a higher strength than conventional biomaterials, as well as to a process for producing said biomaterial.